Affiliations: Department of Clinical Neurology, University of
Sheffield, Sheffield S10 2JF, UK | Department of Psychology, University of Strathclyde,
Glasgow G1 1XQ, UK | Neuroimaging Unit | Brain Image Analysis Unit, Institute of Psychiatry, De
Crespigny Park, London SE5 8AF, UK
Note: [] Corresponding author: Professor A.R. Mayes, Department of
Clinical Neurology, N Floor, Royal Hallamshire Hospital, Sheffield S10 2JF, UK.
Tel.: +44 (0)114 271 3431; Fax: +44 (0)114 276 0095; E-mail:
A.Mayes@Sheffield.ac.uk
Abstract: Neuroimaging studies have shown that memory encoding activates the
medial temporal lobe (MTL). Many believe that these activations are related to
novelty but it remains unproven which is critical - novelty detection or the
rich associative encoding it triggers. We examined MTL activation during verbal
associative encoding using functional magnetic resonance imaging. First,
associative encoding activated left posterior MTL more than single word
encoding even though novelty detection was matched, indicating not only that
associative encoding activates the MTL particularly strongly, but also that
activation does not require novelty detection. Moreover, it remains to be
convincingly shown that novelty detection alone does produce such activation.
Second, repetitive associative encoding produced less MTL activation than
initial associative encoding, indicating that priming of associative
information reduces MTL activation. Third, re-encoding familiar associations in
a well-established way had a minimal effect on both memory and MTL activation,
indicating that MTL activation reflects storage of associations, not merely
their initial representation.
